A Baby Zen V2

jh6you · 11th September 2002, 11:14 AM

A Baby ZV2...?

Having no measurement tool, I mathematically estimated the ac current ratio between R1 and R13/14 of ZV2 (of 30V dc-supply). I got 55.2941%. I did this just for a DIYer¡¯s fun.

By the way, I am stepping back to reduce the bias current from 2 to 1.32A. It is mainly to lower the heatsink temperature. The work for this would be easy by applying 0.5 ohms for all of R1, R13 and R14. Sure, it is a must that I should get back to the 50% ac current ratio, either by replacing R15 with 700 ohms or by replacing R6 with 3.3k ohms.

Meanwhile, I have the following questions.

(A)
This tweak must be worsening the distortion character. Is it however OK if I stay within 8W output, for a 4-ohm speaker?
(B)
If no, what could be menimum bias current for the (A) to be practical?
(C)
Which is better, replacing R15 or R6?

Your advice before I kick my ... would much appreciate.

JH

Nelson Pass · 11th September 2002, 06:31 PM

As you might be able to see from the curves in the
ZV4 article, there is not much degradation into 8 ohms
with the lower bias.

I usually adjust R16, as it doesn't affect the DC.

jh6you · 12th September 2002, 01:45 AM

.

=

!!!

?

Got it... No problem...

JH

jh6you · 15th September 2002, 03:48 AM

Thanks Mr Pass for the advice on R16.
Attached is inner side of my baby ZV4 in case anybody comes in and calls for open discussions.

ZV4 is the summit of Zen variations. Relatively, my baby has a low profile. Nevertheless, the baby is now launched, and on sea trial with a passive pre. I have a plan to post the sea trial results in 10 days.

JH

jh6you · 19th September 2002, 10:50 AM

Hi

The baby is still on the sea trial.

By the way, the circuit is somewhat modified. I re-checked data of IRFP150,
estimated the C(gs) and C(Miller), and got the total C(in) of about 3000 pF.
C(stray) is however ignored. With this high C(in), I wanted the upper critical
frequency beyond about 60 kHz in normal listening. The modification was
a result of this thinking.

I presume the max output power of 15W+15W. If I stay within 10W+10W,
I would not need to think about the distortion much.

I¡¯m continuing my listening trial with TV providing 0.5Vrms output, DVD/CD player
of 2Vrms and tuner of 2Vrms. So far this baby works really better than expected.
Tho I am wondering if this circuit has no technical defects¡¦

Any advice, comment or question¡¦?

In a few days, I¡¯d like to come back with about the sound.

JH

jh6you · 23rd September 2002, 01:27 PM

Hi

Conclusion is made with the baby attached below.

The maximum output power is low.
The heatsink temperature is low. According to the measurement, it is 41.1 degC at the room temperature of 25.5 degC. (230mmx250mmx65mm of 18 fins per channel)
The asymmetric Class A character of Zen might be a bit diminished due to the reduced bias.
However, the naturalness of the sound, as in other Zens, remains the same.
Detailed sound is distinctive, but somewhat dry. I think the dry sound could be improved by using the active preamp, e.g. BOZ.
The overall musical impression is to my satisfaction.

Thank you for your reading.

JH

PS.
The above is with 4-ohm 92dB Ariel speaker. I increased R16 from 700 to 1k ohms to soften the bass a little bit. If I increase R16, it also helps speaker quietness on idling condition.

Nelson Pass · 23rd September 2002, 09:28 PM

The IRF150's have more transconductance than the
140's or 044's, and so R16 will tend to want to be a bit
bigger for optimal performance than as shown in the
original schematic.

jh6you · 24th September 2002, 12:47 PM

Thank you for the advice, Mr Nelson Pass.
If I replace the 150¡¯s with 140¡¯s or 044¡¯s, I¡¯ll come back.

One thing is missed in the above conclusion.
The R19 of 2.7k is sized to scale down the output level.
The full output could be achieved, with R19 of 1.5k
when the input is 2 Vrms.

jh6you · 25th September 2002, 02:31 PM

Finale

At the full output, the load power is 10W.

jh6you · 27th September 2002, 08:56 AM

To whom interested

For me, the best sound performance is finally achieved with 1.5K of R16--i.e. when the AC current through R0 is 30% of the current going through the parallel R14 and 15.

The texture of BEETOVEN SYMPHONIE No5, Wiener Philharmoniker, Carlos Kleiber, was very nice. Also other music¡¯s...

As you might already know well, we could find our sound by tweaking this resistor value not only with the baby, but also with ZV2 and V4. It's another fun... I'm sure it.

11th September 2002, 11:14 AM	#1
jh6you Account Disabled Join Date: Aug 2002 Location: Near to the Pacific Ocean	A Baby Zen V2 A Baby ZV2...? Having no measurement tool, I mathematically estimated the ac current ratio between R1 and R13/14 of ZV2 (of 30V dc-supply). I got 55.2941%. I did this just for a DIYer¡¯s fun. By the way, I am stepping back to reduce the bias current from 2 to 1.32A. It is mainly to lower the heatsink temperature. The work for this would be easy by applying 0.5 ohms for all of R1, R13 and R14. Sure, it is a must that I should get back to the 50% ac current ratio, either by replacing R15 with 700 ohms or by replacing R6 with 3.3k ohms. Meanwhile, I have the following questions. (A) This tweak must be worsening the distortion character. Is it however OK if I stay within 8W output, for a 4-ohm speaker? (B) If no, what could be menimum bias current for the (A) to be practical? (C) Which is better, replacing R15 or R6? Your advice before I kick my ... would much appreciate. JH

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11th September 2002, 06:31 PM	#2
Nelson Pass The one and only Join Date: Mar 2001	As you might be able to see from the curves in the ZV4 article, there is not much degradation into 8 ohms with the lower bias. I usually adjust R16, as it doesn't affect the DC.

12th September 2002, 01:45 AM	#3
jh6you Account Disabled Join Date: Aug 2002 Location: Near to the Pacific Ocean	. = !!! ? Got it... No problem... JH

23rd September 2002, 09:28 PM	#7
Nelson Pass The one and only Join Date: Mar 2001	The IRF150's have more transconductance than the 140's or 044's, and so R16 will tend to want to be a bit bigger for optimal performance than as shown in the original schematic.

24th September 2002, 12:47 PM	#8
jh6you Account Disabled Join Date: Aug 2002 Location: Near to the Pacific Ocean	Thank you for the advice, Mr Nelson Pass. If I replace the 150¡¯s with 140¡¯s or 044¡¯s, I¡¯ll come back. One thing is missed in the above conclusion. The R19 of 2.7k is sized to scale down the output level. The full output could be achieved, with R19 of 1.5k when the input is 2 Vrms.

25th September 2002, 02:31 PM	#9
jh6you Account Disabled Join Date: Aug 2002 Location: Near to the Pacific Ocean	Finale At the full output, the load power is 10W.

27th September 2002, 08:56 AM	#10
jh6you Account Disabled Join Date: Aug 2002 Location: Near to the Pacific Ocean	To whom interested For me, the best sound performance is finally achieved with 1.5K of R16--i.e. when the AC current through R0 is 30% of the current going through the parallel R14 and 15. The texture of BEETOVEN SYMPHONIE No5, Wiener Philharmoniker, Carlos Kleiber, was very nice. Also other music¡¯s... As you might already know well, we could find our sound by tweaking this resistor value not only with the baby, but also with ZV2 and V4. It's another fun... I'm sure it.

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